Many working sites in manufacturing industry have magnetic disks to hoist and move metal work pieces (such as cast iron or steel plate) due to the metal work pieces are heavy and difficult to move manually. The magnetic disk functions based on the interaction between N pole and S pole in which the magnetic lines of force of the same direction repulse each other while those of the opposite directions attract each other. The magnetic attracting force can attract the metal work pieces and move them to desired locations. Then a demagnetization process is performed to unload the work pieces. To accomplish this function a switch is provided on an outer side of the magnetic disk to control the direction of the magnetic lines of force of the N pole and S pole to generate magnetic attraction and demagnetization at the bottom of the magnetic disk. Operation of the switch to generate the magnetic attraction and demagnetization has to be done very carefully without any mistake. When the work pieces are being moved through the magnetic attraction, any improper operation could result in abrupt demagnetization and cause dropping of the work pieces from a high elevation and become dangerous. Hence ON/OFF design of the magnetic disk has to take into account of user operation methods and eliminate the possibility of mistake and abrupt demagnetization.